AAWSAP DIRD, Metamaterials for Aerospace Applications, April 2010

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Applications to Circuits and Waveguide Miniaturization:
Slowing Down and Manipulating Electromagnetic Pulses
(EMP) Using Advanced Metamaterials
Given the space constraints of an advanced aerospace platform and the amount of the
useful payload that has to be carried, it is very important that every optical and
microwave component be as small as possible. Because of the very large speed of light,
there is a natural limit to how small such components can be made. Any structure
capable of processing EMPs (be those optical, THz, or microwave) of temporal duration
r must be at least L =er long. For example, a 1 ns microwave pulse can be
manipulated inside a device that is at least 1 ft long. Pulse manipulation can be
understood very broadly by pulse compression, frequency shifting, harmonics
generation, or other. For aerospace communications systems, it may be very desirable
to have the ability to manipulate the format of EMPs, (that is, to change their
frequency, duration, and repetition rate). Slowing down or even stopping the EMP can
circumvent the length requirement if the group velocity is reduced to vg << c , and thus
the required length is L = vgr.
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Figure 14. Schematic of Pulse Compression in Magnetized Plasma. A radiation pulse with initial frequency
w0 and duration T slows down in the plasma to a group velocity v80 << C. Adiabatic spatially uniform variation
of the magnetic field changes the radiation frequency to W1 and increases the group velocity to v g, >> Vgo. The
emerging pulse is compressed to I; =Tv80 I v8 1 . (Reference 29)
An example of the pulse slowing down and subsequent manipulation is first discussed in
Reference 29 in the somewhat esoteric context of magnetized plasma. Pulse duration,
frequency, and (for multiple pulses) repetition rate can be controlled by storing (or
slowing down) electromagnetic waves and subsequently changing the system's
parameters. The essence of the compact pulse manipulator is shown in Figure 14. The
pulse is slowed down inside the compact plasma device and manipulated by changing
the magnitude of the magnetic field. The advantage of slowing the pulses down is
three-fold. First, the device can be made smaller, resulting in size savings. Second, the
temporal scale on which the system has to be manipulated is lengthened because the
pulse is moving slowly. Finally, the potentially large ratio between v81 >> vgo results in
the more dramatic dynamic range of possible pulse compression ratios. Plasma-based
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